JP4818383B2 - Relay device and method for registering cache data in the same device - Google Patents

Description

  The present invention relates to a relay device that relays communication for data transfer between a first device that stores data and a second device that performs read / write access to the first device, and is particularly cacheable. The present invention relates to a relay apparatus suitable for registering various data as cache data and a method for registering cache data in the apparatus.

  Recently, for example, information leakage from a client personal computer (hereinafter referred to as a client PC) used as a client device in a company or a public office has become a problem. Therefore, a thin client system has attracted attention as a computer system for preventing the client PC from taking out information.

  Thin client systems are classified into several types according to their implementation methods. As one of thin client systems, a network boot type thin client system is known. In a network boot type thin client system, a storage device is arranged in a server room where there is little concern about information leakage physically. The client PC uses a communication protocol such as NFS (Network File System), CIFS (Common Internet File System), or iSCSI (Internet Small Computer System Interface) to and from this storage device to directly execute an OS from the storage device. Boot (Operating System).

  One of the challenges of the network boot thin client system is that in the environment where the client PC and the storage device are connected by a WAN (Wide Area Network), the slowness of the WAN line speed becomes a bottleneck. It is known that it is difficult to introduce. Therefore, like a proxy in the world of WWW (World Wide Web), a relay device (node device) is introduced between the storage device and the client PC, and the data relayed by the relay device is used as cache data. A technique has been proposed in which load control is performed and performance is improved by performing cache control for storing data in a cache data storage unit (cache data storage unit) on the relay device. However, it is necessary to consider how to implement a countermeasure against information leakage from the cache data storage means as a new problem caused by performing cache control in the relay device.

  For example, Patent Document 1 describes a technique for realizing a countermeasure against information leakage from a cache data storage unit of a relay device. In the technique described in Patent Document 1, the client PC or the storage device outputs attribute information indicating whether or not the cache is possible for data relayed by the relay device. The relay device determines whether or not to cache the data to be relayed based on the attribute information, and does not store the data determined to be cache (eg, confidential data) without storing it in the cache data storage means, that is, without caching. And only relay. According to such a technique described in Patent Document 1, since it is possible to prohibit the confidential data from being cached in the relay device, it is possible to prevent the confidential data from leaking from the relay device (the cache data storage unit thereof).

JP 2004-287476 A

  In Patent Document 1, each time data is transferred between the client device and the storage device, attribute information indicating whether or not the data can be cached is added to the data (header) and notified to the relay device. (Hereinafter referred to as the first technique). Patent Document 1 also describes that attribute information managed for each data in the storage apparatus is notified from the storage apparatus to the relay apparatus separately from the data transfer (hereinafter referred to as a second method). Has been.

  The first method has a problem that attribute information must be notified every time data is transferred between a client device and a storage device. On the other hand, the second method has a problem that attribute information managed for each data must be notified (transferred) from the storage apparatus to the relay apparatus separately from the data transfer.

  The present invention has been made in consideration of the above circumstances, and its purpose is to perform relaying that can efficiently register cacheable data without requiring notification to the relay device of attribute information indicating whether data can be cached. To provide a device and a method for registering cache data in the device.

  According to one aspect of the present invention, a relay device that relays communication for data transfer between a first device that stores data and a second device that performs read / write access to the first device Is provided. The relay device stores data stored in the first device in association with an identifier corresponding to the content of the data, and content of the data stored in the cache storage device And a cache index table for holding an identifier corresponding to the index in the first device in association with an index designating the data, and a cache that receives a cache registration request including the index transmitted from the third device A registration request receiving means and a relay means for relaying communication for data transfer between the first device and the second device, wherein the cache registration request receiving means receives the cache registration request In the first case, the first data specified by the index included in the cache registration request is stored in the first device. In the second case of receiving a read / write request including an index for reading / writing access from the second device to the first device, a second corresponding to the index included in the read / write request is received. Relay means for inputting / outputting data to / from the second device, identifier generating means for generating an identifier corresponding to the content of the requested data, and in the first case, the content of the first data A corresponding identifier is generated by the identifier generation unit, the first data is stored in the cache storage unit in association with the generated identifier, and the generated identifier is designated as the first data Cache registration means for registering in the cache index table in association with an index to be included, and in the second case, included in the read / write request A cache hit determination means for determining whether a cache hit is made depending on whether an identifier is registered in the cache index table in association with the index and an identifier identical to the identifier is registered in the cache storage means; When it is determined that it is not a cache hit, the relay unit relays the read / write request to the first device, thereby relaying the second data designated by the index included in the read / write request. And generating the identifier corresponding to the content of the second data relayed by the relay means by the identifier generating means, The cache storage means in association with the assigned identifier. And index registration means for registering the generated identifier in the cache index table in association with the index included in the read / write request when the same data as the data of 2 is stored. It is characterized by.

  According to the present invention, cacheable data can be efficiently registered without requiring notification to the relay device of information indicating whether data can be cached. In particular, according to the present invention, in response to a cache registration request, an identifier corresponding to the content of data specified by an index included in the cache registration request is registered in the cache index table in association with the index, And if the data is stored in the cache storage means in association with the identifier, that is, registered as cache data, the read / write request from the second device will include If the same data as the data specified by another index (that is, the data specified by the read / write request) is already registered as cache data in association with the identifier corresponding to the content of the same data, The specified data is also automatically registered as cache data.

1 is a block diagram showing the overall configuration of a computer system according to an embodiment of the present invention. The block diagram which shows the basic composition of the computer used for the storage apparatus and relay apparatus which are shown by FIG. 2 is an exemplary block diagram illustrating functional configurations of a storage apparatus, a client apparatus, and a relay apparatus in the embodiment. FIG. The figure which shows the data structure example of the cache index table in the same embodiment. The figure which shows the data structure example of the cache data table in the embodiment. The figure for demonstrating the relationship between a cache index table, a cache data table, and a cache data storage part. 6 is a flowchart showing a procedure of a cache registration operation in the embodiment. 6 is an exemplary flowchart illustrating a processing procedure of the relay apparatus when the client apparatus reads data from the storage apparatus in the embodiment. 6 is an exemplary flowchart illustrating a procedure of registration processing in a cache index table according to the embodiment. 9 is a flowchart showing a procedure of a cache registration operation in a modification of the embodiment. The flowchart which shows the procedure of the session acquisition process in the modification.

Embodiments of the present invention will be described below with reference to the drawings.
<System configuration>
FIG. 1 is a block diagram showing the overall configuration of a computer system according to an embodiment of the present invention. This computer system is, for example, a thin client system (more specifically, a network boot type thin client system). The system shown in FIG. 1 includes a storage device (first device) 10, a plurality of client devices including a client device (second device) 20, and a relay device 30. In FIG. 1, client devices other than the client device 20 are omitted for convenience.

  The storage apparatus 10 has n disk volumes 100-1 to 100-n (see FIG. 3) for storing various data. In the present embodiment, n disk volumes 100-1 to 100-n are prepared in association with n client apparatuses including the client apparatus 20, respectively. Here, it is assumed that the disk volume 100-1 is associated with the client device 20. The storage apparatus 10 provides access to the corresponding disk volume to each of a plurality of client apparatuses including the client apparatus 20. The storage device 10 has a function as a target in iSCSI, for example.

  The disk volumes 100-1 to 100-n may be prepared in association with, for example, n users who use a plurality of client devices including the client device 20, respectively. Also, a plurality of disk volumes may be associated with one client device (one user), and the number of disk volumes associated with each of n client devices (n users) is the client device (user). ) May be different for each.

  The client device 20 accesses the storage device 10. More specifically, among the disk volumes 100-1 to 100-n in the storage apparatus 10, the disk volume associated with itself (here, the disk volume 100-1) is accessed. The client device 20 functions as an initiator in iSCSI, for example.

  The relay device 30 relays communication between a plurality of client devices (initiators) including the client device 20 and the storage device 10 (target), for example, data transfer by the iSCSI protocol. The iSCSI protocol is a protocol for carrying the SCSI protocol used in the storage apparatus 10 using TCP (Transmission Control Protocol) / IP (Internet Protocol). The relay device 30 performs cache control of data to be transferred when relaying data transfer by the iSCSI protocol.

  In the present embodiment, the storage device 10 and the relay device 30 are realized using a computer. FIG. 2 is a block diagram showing the basic configuration of such a computer. As shown in FIG. 2, the computer has a known hardware configuration of at least one processing unit 21, main storage device 22, auxiliary storage device 23, communication mechanism 24, and input / output device 25. The auxiliary storage device 23 is configured using, for example, a hard disk drive. A program executed by the processing unit 21 can be stored in the auxiliary storage device 23. The communication mechanism 24 performs communication for data transfer according to the iSCSI protocol.

  The client device 20 is also realized using a computer. However, the client device 20 does not include the auxiliary storage device 23 shown in FIG. That is, the client device 20 has a hardware configuration excluding the auxiliary storage device 23 in the hardware configuration of the computer shown in FIG. Therefore, in the client device 20, among the programs executed by the processing unit 21, for example, a program transferred from the storage device 10 (a program including an OS in the present embodiment) is stored in the main storage device 22. Note that a program for requesting later-described cache registration from the client device 20 to the relay device 30 (hereinafter referred to as a specific program) is stored in advance in, for example, a ROM.

FIG. 3 is a block diagram illustrating functional configurations of the storage apparatus 10, the client apparatus 20, and the relay apparatus 30 in the system of FIG.
In FIG. 3, the storage apparatus 10 has disk volumes 100-1 to 100-n. Each disk volume 100-i (i = 1 to n) is realized by using the storage area of the auxiliary storage device 23 shown in FIG. In this embodiment, each disk volume 100-i is a logical unit (logical volume) that provides a logical address space. Each disk volume 100-i is assigned a unique ID (serial number) called a disk volume number DVN.

  The client device 20 includes a driver / file system 210 and a cache registration data selection / request transmission unit 220. In this embodiment, the driver file system 210 is a processing unit in a computer when the client device 20 is configured from a computer having a hardware configuration excluding the auxiliary storage device 23 from the configuration shown in FIG. 21 is realized by executing a program (for example, OS) downloaded from the storage device 10 to the main storage device 22 of the client device 20. On the other hand, the cache registration data selection / request transmission unit 220 is realized, for example, when the processing unit 21 reads and executes a specific program stored in advance in the ROM in the main storage device 22.

  The driver file system 210 constructs the file system 211 from the disk volume 100-1 in the storage apparatus 10 associated with the client apparatus 20, for example. The file system 211 specifies information (hereinafter referred to as a data area) in the disk volume 100-1 in which the corresponding file is stored from the file path to the cache registration data selection / request transmission unit 220. Hereinafter, an interface for obtaining data area information) is provided.

  In the present embodiment, the start position of the data area matches the start position of the logical block (logical block boundary), and the end position of the data area matches the logical block end position (logical block boundary). And Therefore, the data area information includes a logical block address (hereinafter referred to as a start logical block address) LBA at the start position of the data area, and information on the data length (size) L of the data area (file stored in the data area). including. This data length L is an integral multiple of the data length of the logical block.

  The cache registration data selection / request transmission unit 220 performs relaying based on the operation of the user (or system administrator) using the input / output device 25 (see FIG. 2) included in the hardware configuration of the client device 20, for example. The designation of data (here, a file) to be registered as cache data in the apparatus 30 is accepted. Based on this designation, the cache registration data selection / request transmission unit 220 sends data area information LBA / L regarding the data area in the disk volume (here, the disk volume 100-1) in which the file is stored from the file system 211. And the information LBA / L is transmitted to the relay device 30 by a cache registration request.

  The relay device 30 mainly performs two types of operations. The first operation is a cache registration operation for registering data transferred from the storage device 10 as cache data in response to a cache registration request transmitted from the cache registration data selection / request transmission unit 220 of the client device 20. The second operation is performed in response to a read / write request (read request or write request) transmitted from the driver file system 210 of the client device 20, and input / output (I / O) between the storage device 10 and the client device 20. O) Relay of session (here, iSCSI session) and cache operation.

  The relay of the iSCSI session is performed as follows. First, the client device 20 specifies the client device side interface (I / F) 311 of the relay device 30 and requests connection to the storage device 10. When receiving the request from the client device 20, the relay device 30 connects to the storage device 10 from the storage device side interface (I / F) 312 of the relay device 30. Thereby, a connection (iSCSI session) between the client device 20 and the storage device 10 is established via the relay device 30. Note that the client device side interface 311 and the storage device side interface 312 may be physically one interface. If iSCSI, the TCP / IP IP address and port number are separate interfaces. It is enough if can be identified. The interfaces 311 and 312 are realized by the communication mechanism 24.

<Configuration of relay device>
In order to realize the above-described two types of operations, the relay device 30 includes a relay unit 310, a cache management unit 320, a cache index table 330, a cache data table 340, a cache data storage unit 350, an identifier generation unit 360, and a cache registration request. A processing unit 370 is included. In the present embodiment, the relay unit 310, the cache management unit 320, the identifier generation unit 360, and the cache registration request processing unit 370 in the relay device 30 are configured when the relay device 30 includes the computer illustrated in FIG. The processing unit 21 in the computer is realized by reading a predetermined program stored in the auxiliary storage device 23 into the main storage device 22 and executing it.

  The relay unit 310 relays PDU (Protocol Data Unit) transfer between the client apparatus 20 and the storage apparatus 10 according to the iSCSI protocol, that is, transfer of iSCSI-PDU. The relay unit 310 includes a client apparatus side interface 311 and a storage apparatus side interface 312. If the iSCSI-PDU is related to data transfer (READ & SCSI DATAIN / WRITE & SCSI DATAOUT), cache control by the cache management unit 320 is performed.

  The cache management unit 320 performs cache control of data relayed by the relay unit 310 in response to a read request or a write request from the driver / file system 210 of the client device 20. The cache management unit 320 performs a cache registration operation for registering data designated by the cache registration request transmitted from the cache registration data selection / request transmission unit 220 of the client device 20 in the relay device 30 as cache data.

  The cache management unit 320 manages the cache index table 330 and the cache data table 340. The cache management unit 320 also manages the cache data storage unit 350. The cache management unit 320 includes a cache registration unit 320a, a cache hit determination unit 320b, a relay control unit 320c, and an index registration unit 320d.

  The cache index table 330 is provided in association with the disk volume (logical volume) 100-i in the storage apparatus 10. The cache index table 330 includes a combination of a disk volume number DVN unique to a corresponding disk volume 100-i and a logical block address LBA of a logical block in the disk volume 100-i stored in the logical block. Is stored as an index to specify. The cache index table 330 holds an identifier corresponding to the content of data specified by this index in association with the index.

  The disk volume number DVN is a number for identifying the corresponding disk volume 100-i. In this embodiment, the disk volume number DVN is serially assigned to all the disk volumes 100-i in the relay apparatus 30. This disk volume number DVN is acquired by issuing a CDB (Command Descriptor Block) for inquiry from the relay device 30 to the storage device 10. In the case of iSCSI, instead of DVN, a combination of the DVN and iSCSI-InitiatorName (initiator name) can be used.

  FIG. 4 shows an exemplary data structure of the cache index table 330. In the example of FIG. 4, the cache index table 330 has a group of entries. The cache index table 330 holds a disk volume number DVN unique to the corresponding disk volume 100-i independently from the entry group. Each entry in the cache index table 330 holds a logical block address LBA of a logical block in the corresponding disk volume 100-i and an identifier corresponding to the content of data (block data) stored in the logical block. .

  As described above, the cache index table 330 shown in FIG. 4 includes each index for designating data of a logical block in the disk volume 100-i, a disk volume number DVN common to each index, and each index. Are separated into different logical block addresses LBA. This reduces the storage capacity required for each entry in the cache index table 330. The disk volume number DVN held in the cache index table 330 independently from the entry group of the table 330 constitutes an index in combination with the logical block address LBA held in each of the entry group. Therefore, it can be said that each entry of the cache index table 330 equivalently holds a pair of an index and an identifier.

  The identifier held in each entry of the cache index table 330 is, for example, the logical block address LBA in the corresponding index when a is an integer greater than 0 representing the data length (sector length in this case) of the logical block. This is a hash value of data for a sector (a multiple of 512 bytes) stored in the specified logical block. As described above, in this embodiment, it is assumed that the data length (size) of the cache block managed by the cache index table 330 (and the cache data table 340) is equal to the data length of the logical block. Of course, it is also possible to equally divide a logical block into a plurality of blocks and manage each equally divided block as a cache block. Furthermore, in this embodiment, for simplicity of explanation, it is assumed that a is 1, and one entry of the cache index table 330 (and the cache data table 340) is managed in units of one sector (= 512 bytes). .

  The cache index table 330 is prepared for each disk volume (logical volume) 100-i in the storage apparatus 10. In other words, the relay device 30 has a cache index table 330 corresponding to the number of disk volumes 100-i on the storage device 10 to which access is relayed by the relay device 30.

  The cache data table 340 uses a hash value of data for a (a = 1 in this embodiment) sectors managed by the cache index table 330 as an identifier, and the identifier and the data (cache data in the cache data storage unit 350). ) Has a group of entries that hold a pair with a storage (registration) destination address. That is, the cache data table 340 is a set of an identifier held in association with the logical block address LBA in an entry of the cache index table 330 and a storage address of the corresponding cache data (hereinafter referred to as a cache data address). Has a group of entries. FIG. 5 shows an example of the data structure of the cache data table 340.

  In the following description, registering an identifier (including entry information) corresponding to the content of data (cache data) stored in the cache data storage unit 350 in an entry of the cache data table 340 is described in the cache data table 340. Sometimes expressed as registering data. In addition, the identifier (including entry information) corresponding to the content of the data stored in the cache data storage unit 350 is registered in the entry of the cache data table 340, and the data is registered in the cache data table 340. Sometimes expressed. That is, the cache index table 330 and the cache data table 340 constitute a cache storage unit 380 for storing data stored in the disk volume 100-i of the storage apparatus 10 in association with an identifier corresponding to the content of the data. To do.

  For example, the cache index table 330 and the cache data table 340 are used by being stored in a part of the storage areas of the main storage device 22 and the auxiliary storage device 23 included in the hardware configuration of the relay device 30. The cache data storage unit 350 is realized by using a part of the storage areas (volatile storage area and nonvolatile storage area) of the main storage device 22 and the auxiliary storage device 23. Specifically, the tables 330 and 340 are stored and used in the main storage device 22 in the operation state of the relay device 30, and are stored in the auxiliary storage device 23 at least when the operation of the relay device 30 is stopped. . The tables 330 and 340 are loaded from the auxiliary storage device 23 to the main storage device 22 when the relay device 30 is activated. The same applies to the data stored in the cache data storage unit 350. However, such a form is an example, and for example, only one of the main storage device 22 (volatile storage device) and the auxiliary storage device 23 (nonvolatile storage device) may be used.

  In the present embodiment, the cache index table 330 and the cache data table 340 are described by taking the block type transfer protocol by iSCSI as an example, but the present invention is not limited to iSCSI. For example, by using a path name as an index, a file transfer protocol such as NFS (Network File System) or CIFS (Common Internet File System) can be applied instead of the block transfer protocol based on iSCSI.

  The cache data storage unit 350 stores cache data for a (= 1) sectors at the cache data address managed by each entry of the cache data table 340. The hash value of the cache data matches the identifier held in the corresponding entry of the cache data table 340 in pairs with the cache data address.

  Next, the relationship among the cache index table 330, the cache data table 340, and the cache data storage unit 350 will be described with reference to FIG. In FIG. 6, unlike FIGS. 4 and 5, the disk volume number DVN, logical block address LBA, identifier (hash value), and identifier stored (registered) in the cache index table 330 and the cache data table 340 The cache data address is simplified for convenience.

  FIG. 6 illustrates a cache index table 330 corresponding to a disk volume in the storage apparatus 10 identified by the disk volume number “DVN1”, for example, the disk volume 100-1.

  In the first entry of the cache index table 330, the identifier “hash value 1” is registered in association with the logical block address “LBA1”. In the second, third and fourth entries of the cache index table 330, the identifier “hash value 2” is associated with the logical block address “LBA2”, and the identifier “HBA3” is associated with the identifier “ The identifier “hash value 1” is registered in association with the hash value 3 ”and the logical block address“ LBA4 ”. That is, the data stored in the logical block address “LBA1” and the data stored in the logical block address “LBA4” are the same. In other words, the logical block addresses “LBA1” and “LBA4” held in the cache index table 330 indicate the same data.

  On the other hand, in the first entry of the cache data table 340, “address 1” is registered as a cache data address in association with the identifier “hash value 1”. In the second and third entries of the cache data table 340, “address 2” is associated with the identifier “hash value 2” as the cache data address, and cache is associated with the identifier “hash value 3”. “Address 3” is registered as the data address. That is, the first, second, and third entries of the cache data table 340 include data corresponding to the identifiers “hash value 1”, “hash value 2”, and “hash value 1” (here, data A, data B and data C) are registered. These data are data that can be leaked without any problem.

  Further, data A is stored at “address 1” of the cache data storage unit 350. Data B and data C are stored in “address 2” and “address 3” of the cache data storage unit 350, respectively.

  The data A is data cached at “address 1” in the cache data storage unit 350, and the logical block address “of the disk volume 100-1 in the storage apparatus 10 identified by the disk volume number“ DVN1 ”. LBA1 ”and data stored in the logical block address“ LBA4 ”.

  The data B is data cached at “address 2” in the cache data storage unit 350, and the logical block address “LBA2” of the disk volume 100-1 in the storage apparatus 10 identified by the disk volume number “DVN1”. Is the same as the data stored in

  The data C is data cached at “address 3” in the cache data storage unit 350, and the disk volume serial number “1” of the storage apparatus 10 in the storage apparatus 10 identified by the disk volume number “DVN1”. Data stored in the logical block address “3” of “”.

  As described above, the cache index table 330 and the cache data table 340 are associated by an identifier (hash value). Thereby, for example, when there is a read request from the storage apparatus 10 to the storage apparatus 10, the relay apparatus 30 transfers the index (disk volume serial number and logical block address) included in the read request to the cache data storage unit 350. The cache data stored (cached) can be specified.

  Referring to FIG. 3 again, the identifier generation unit 360 receives the data for a sector from the cache management unit 320, generates an identifier corresponding to the content of the data, and sends the generated identifier to the cache management unit 320. respond. In this embodiment, a predetermined hash function is used for generating the identifier. For this hash function, MD (Merkle-Damgard) 5 or SHA (Secure Hash Algorithm) 1 can be used.

  The cache registration request processing unit 370 receives as input from the cache registration data selection / request transmission unit 220 in the client device 20 the logic of the initiator name of the client device 20 and data (for example, a file) to be registered as cache data. The block address LBA and the data length (number of sectors) L are received (including a cache registration request). For simplicity of explanation, it is assumed that the data length L is an integer multiple of the data length of the logical block.

  Upon receiving this input, the cache registration request processing unit 370 generates an iSCSI-PDU for receiving the data specified by the logical block address LBA and the data length L in the iSCSI session corresponding to the initiator name. .

  The cache registration request processing unit 370 transmits the generated iSCSI-PDU to the storage device 10 in cooperation with the relay unit 310. By transmitting the iSCSI-PDU, the cache registration request processing unit 370 receives the data in the data area specified by the logical block address LBA and the data length L notified from the storage apparatus 10 by the iSCSI-PDU. The cache registration request processing unit 370 registers the received data information in the cache index table 330 and the cache data table 340 in cooperation with the cache management unit 320.

<Outline of operation of relay device>
First, an outline of the operation centering on the relay device 30 will be described.
The relay device 30 switches operation depending on whether or not the iSCSI-PDU relayed by the relay device 30 is related to data transfer. First, if the iSCSI-PDU to be relayed is not related to data transfer, the relay device 30 performs an operation of transferring the iSCSI-PDU as it is to the other party. On the other hand, if the iSCSI-PDU is related to data transfer, the relay device 30 performs a cache access operation through the cache management unit 320.

  In addition, the relay device 30 performs the following two types of operations. One of the two types of operations is a cache registration operation for registering cache data in the relay device 30. Another one of the two types of operations is an iSCSI session relay operation for relaying an iSCSI session (input / output session) from the client device 20 to the storage device 10. When this iSCSI session relay operation is performed, a cache operation described later is also performed.

<Cache registration operation>
Next, a cache registration operation for registering cache data in the relay device 30 will be described.

First, an overview of the cache registration operation will be described.
In the present embodiment, the cache registration operation includes the following two procedures 1 and 2.
Procedure 1: The cache registration data selection / request transmission unit 220 of the client device 20 transmits an index of data to be cache registered to the relay device 30 in response to a cache registration request.

  Procedure 2: When the cache registration request processing unit 370 of the relay device 30 receives an index (including a cache registration request) from the cache registration data selection / request transmission unit 220 of the client device 20, the cache registration request processing unit 370 uses the relay unit 310 to Is read from the storage device 10. The cache management unit 320 of the relay device 30 stores the read data as cache data in the cache data storage unit 350 and adds new entry information to the cache index table 330 and the cache data table 340 for managing the cache data. Register. However, if the entry information is already registered in the tables 340 and 340, the new entry information is not registered.

Next, the details of the procedures 1 and 2 will be described with reference to the flowchart of FIG.
<Details of Procedure 1>
First, details of the procedure 1 will be described.
Now, it is assumed that a plurality of files stored in the disk volume 100-1 are managed by the file system 211 of the client apparatus 20. It should be noted that this file system 211 is composed of a disk volume 100-1 on the storage apparatus 10.

  The cache registration data selection / request transmission unit 220 of the client device 20 includes one or more items to be registered as cache data in the relay device 30 from the files managed by the file system 211 of the client device 20. A file is determined (step 700). For the determination of this file, for example, cache registration data from the user of the client device 20 or the system administrator using the input / output device 25 (see FIG. 2) included in the hardware configuration of the client device 20 Various methods such as explicit designation for the selection / request transmission unit 220 and automatic determination based on a file name can be applied. Here, it is assumed that a file name is specified. In step 700, the address (for example, IP address) of the relay apparatus 30 that is the cache registration destination is also designated.

  That is, in step 700, the cache registration data selection / request transmission unit 220 inputs the designation of the file name of the cache registration target file, and determines the cache registration target file. In step 700, the cache registration data selection / request transmission unit 220 also inputs the designation of the address of the cache registration destination relay device 30.

  The cache registration data selection / request transmission unit 220 identifies the disk volume number DVN for identifying the disk volume 100-1 in which the specified cache registration target file is stored, and the disk volume 100- in which the file is stored. Data area information LBA / L designating the data area in i is acquired through the file system 211 of the client device 20 (step 701). Here, for simplification of description, it is assumed that the data length L of the data area (file) is a (= 1) sector that matches the length of one logical block.

  Next, the cache registration data selection / request transmission unit 220 transmits a cache registration request for requesting registration of cache data to the cache registration request processing unit 370 of the designated relay device 30 (step 702). This cache registration request includes an index indicating data (file data in this case) that is a target of cache registration. This index includes the disk volume number DVN and logical block address LBA acquired in step 701. The cache registration request further includes information on the data length L of the data that is the target of cache registration acquired in step 701 (hereinafter referred to as cache registration target data). That is, the cache registration request includes the disk volume number DVN and the data area information LBA / L.

  Note that the cache registration data selection / request transmission unit 220 may be provided in a device independent of the client device 20 that accesses the storage device 10 (hereinafter referred to as a third device). However, in this embodiment, the cache registration data selection / request transmission unit 220 is provided in the client device 20, that is, the client device 20 (second device) also serves as the third device. The client device 20 (internal cache registration data selection / request transmission unit 220) itself can determine the data that needs to be registered and request the relay device 30 to perform cache registration.

<Details of step 2>
Next, details of the procedure 2 will be described.
The cache registration request processing unit 370 of the relay device 30 functions as a cache registration request receiving unit, and receives the cache registration request transmitted from the cache registration data selection / request transmission unit 220 of the client device 20 (step 703).

  When the cache registration request processing unit 370 receives the cache registration request (step 703), the cache registration request processing unit 370 adds to the disk volume 100-1 of the storage apparatus 10 specified by the disk volume number DVN in the index included in the cache registration request. The relay device 30 is connected through the relay unit 310 (step 704). Here, the disk volume 100-1 connected to the relay apparatus 30 matches the disk volume of the storage apparatus 10 currently connected from the client apparatus 20 that requested the cache registration. In the connection operation in step 704, a session independent of the iSCSI session between the client apparatus 20 and the storage apparatus 10 that is currently being relayed by the relay apparatus 30 is established. The session establishment in step 704 may be performed before the cache registration is requested from the cache registration data selection / request transmission unit 220 of the client device 20, that is, in advance.

  In a state where the above-described session is established by execution of step 704, the cache registration request processing unit 370 generates a read command for reading the cache registration target data requested for cache registration from the client device 20 (step 705). In step 705, the cache registration request processing unit 370 transmits the generated read command to the storage apparatus 10 via the relay unit 310.

  Based on the read request transmitted via the relay unit 310, the storage device 10 reads the requested data from the disk volume 100-1 and returns it to the relay unit 310. The cache registration request processing unit 370 acquires the data returned to the relay unit 310 as cache registration target data via the relay unit 310 (step 706). In this way, the cache registration request processing unit 370 performs cache registration target data (here, the data area specified by the logical block address LBA and the data length L in the disk volume 100-1 specified by the disk volume number DVN). Data for a sector) stored in.

  The cache registration request processing unit 370 passes the acquired cache registration target data to the cache management unit 320 and instructs a cache registration operation designated by the cache registration request received in step 703. Then, the cache registration unit 320a of the cache management unit 320 passes the cache registration target data to the identifier generation unit 360 and requests generation of the identifier of the data.

  The identifier generation unit 360 generates a hash value of the cache registration target data using a predetermined hash function, and returns the generated hash value to the cache registration unit 320a of the cache management unit 320 as an identifier of the data (step 707). . That is, the identifier generation unit 360 generates the acquired hash value of the cache registration target data as the requested identifier. It is assumed that cache registration target data among the relay unit 310, the cache management unit 320, the identifier generation unit 360, and the cache registration request processing unit 370 is exchanged via a buffer (not shown). In this case, physical movement of cache registration target data does not necessarily occur.

  The cache registration unit 320a uses the cache index table 330 (the disk volume 100-1 storing the data acquired in step 705) as the first and second entry information including the identifier generated by the identifier generation unit 360. Are registered in the cache index table 330) and the cache data table 340 (step 708). However, when an entry including an identifier that matches the generated identifier already exists in the cache data table 340, the first and second entry information is not registered.

  The first entry information includes a logical block address LBA that forms part of the index and a generated identifier. The cache index table 330 holds the disk volume number DVN included in this index. Therefore, registering the first entry information in the cache index table 330 is equivalent to registering an identifier in the table 330 in association with the index.

  The second entry information includes a generated identifier and an address (cache data address) of the cache data storage unit 350 in which data indicated by the identifier is stored as cache data. In step 708, the cache registration unit 320a stores the data indicated by the identifier as cache data in the area of the cache data storage unit 350 specified by the cache data address. The first and second entry information may be registered after the cache data is stored.

  When the processing in step 708 by the cache registration unit 320a is completed, the cache registration request processing unit 370 closes the session established in step 704 and then completes the cache registration to the cache registration data selection / request transmission unit 220 of the client device 20. A response is returned (step 709).

  If a plurality of files are designated as input to the cache registration data selection / request transmission unit 220, the above-described steps 701 to 709 are repeated for all the designated files (step 710).

  As described above, in this embodiment, the relay device 30 simply executes the cache registration request from the client device 20, and reads only the data specified by the index included in the request from the storage device 10 to Data can be registered in the relay device 30 as data. For this reason, in this embodiment, unlike the prior art, every time data is transferred between the client device and the storage device, the attribute information is notified or the attribute information managed for each data is transferred to the data. Apart from this, there is no need to notify (transfer) the storage apparatus to the relay apparatus. In this embodiment, the data specified by the cache registration request from the client device 20 is data that does not cause a problem even if leaked, such as an OS file or an application program file.

<ISCSI session relay and cache operation between client / storage device>
In the present embodiment, the relay device 30 relays an iSCSI session as an input / output (IO) session between the client device 20 and the storage device 10. At the time of this relay, the relay device 30 uses the cache index table 330 and the cache data table 340, that is, the cache (cache control) operation using the cache data specified by the entry information registered in both the tables. I do.

Hereinafter, the processing procedure of the relay device 30 when the client device 20 reads data from the storage device 10 will be described with reference to the flowchart of FIG.
Now, it is assumed that the relay unit 310 of the relay device 30 has received the read request transmitted from the client device 20 (step 801). This read request includes an index indicating data to be read (hereinafter referred to as read target data). This index includes a disk volume number DVN for identifying the disk volume 100-i in which the read target data is stored and a logical block address (start logic) indicating the start position of the area in the disk volume 100 in which the read target data is stored. Block address) LBA. The read request further includes information on the data length L of the data to be read. That is, the read request includes the disk volume number DVN and the data area information LBA / L. Here, for simplification of explanation, the data length L of the read target data is a (= 1) sector, is equal to the data length of one cache block, and the data length of one cache block is data of one logical block. It shall be equal to the length.

When the relay request is received by the relay unit 310, the cache hit determination unit 320b of the cache management unit 320 executes the following cache hit determination process based on the index included in the read request (step 802).
First, the cache management unit 320 selects the cache index table 330 associated with the disk volume indicated by the disk volume number DVN included in the index (step 802a). Here, it is assumed that the cache index table 330 associated with the disk volume 100-1 is selected.

  Next, the cache hit determination unit 320b refers to the cache index table 330 and determines whether an identifier is registered (there is an entry) in association with the logical block address LBA included in the index (step 802b).

  If the identifier is registered (YES in step 802b), the cache hit determination unit 320b determines whether the identifier (identical to the identifier) is registered in the cache data table 340 (step 802c). If this identifier is also registered in the cache data table 340 (YES in step 802c), that is, if data corresponding to this identifier is registered in the cache data table 340, the cache hit determination unit 320b. Determines that the data to be read is a cache hit existing in the cache data storage unit 350 (step 802d).

  When the cache hit determination unit 320b determines a cache hit, the relay control unit 320c of the cache management unit 320 sets the cache data address registered in the cache data table 340 in association with the identifier used for the cache determination. Obtain (step 803). Then, based on the acquired cache data address, the relay control unit 320c reads the cache data stored in the cache data address of the cache data storage unit 350 as data to be read (step 804). The relay control unit 320c instructs the relay unit 310 to return the read data to the client device 20 that is the read request source.

  Then, the relay unit 310 transmits the data read from the cache data storage unit 350 by the relay control unit 320c to the client device 20 as a response to the read request from the client device 20 (step 805). Thereby, the processing in the relay device 30 for the read request transmitted from the client device 20 ends.

  On the other hand, if the identifier is not registered in the cache index table 330 (NO in step 802b), the cache hit determination unit 320b determines that the read target data does not exist in the cache data storage unit 350 (step 802e). ). Even if an identifier is registered in the cache index table 330 (YES in step 802b). When the identifier (identical to the same identifier) is not registered in the cache data table 340 (NO in Step 802c), the cache hit determination unit 320b determines that it is a cache miss hit (Step 802e).

  When the cache hit determination unit 320b determines a cache miss hit, the relay control unit 320c relays (transfers) the read request to the storage apparatus 10 via the relay unit 310 (step 806). In response to the read request relayed by the relay unit 310, the storage apparatus 10 reads the read target data from the disk volume 100-1 and returns it to the relay unit 310. As a result, the relay unit 310 acquires data to be read (step 807).

  The relay unit 310 transmits the acquired data to the client device 40 as a response to the read request from the client device 20 (step 808).

  The index registration unit 320d of the cache management unit 320 is a cache index described below for registering an identifier corresponding to the content of the data acquired by the relay unit 310 in the cache index table 330 when a cache miss is determined. A table registration process is executed (step 809). Thereby, the processing in the relay device 30 for the read request transmitted from the client device 20 ends.

Next, the procedure of the registration process to the cache index table (step 809 in FIG. 8) will be described with reference to the flowchart in FIG.
The index registration unit 320d generates the hash value of the data acquired by the relay unit 310 as an identifier corresponding to the content of the data (Step 901). The index registration unit 320d determines whether data corresponding to the generated identifier is registered in the cache data table 340 (step 902). Here, the entry information including the generated identifier (identifier that matches the identifier) is held in the cache data table 340 and stored in the area of the cache data storage unit 350 specified by the cache data address in the entry information. If the cached data and the data acquired by the relay unit 310 are the same, the determination in step 902 is YES. Otherwise, the determination at step 902 is NO.

  When the data corresponding to the generated identifier is registered in the cache data table 340 (YES in Step 902), the index registration unit 320d includes the index in the cache index table 330 used for determining the cache miss. The identifier is registered in association with the logical block address LBA (step 903). The cache index table 330 holds the disk volume number DVN included in the index. Therefore, the processing in step 903 is equivalent to registering an identifier in the cache index table 330 in association with the index. This step 903 will be described in more detail.

Step 903 is roughly divided into a first process and a second process.
The first process is executed when another identifier is already registered in the above-described cache index table 330 in association with the logical block address LBA in the index. In the first process, the generated identifier is registered instead of the other identifier. That is, the registered identifier is replaced with the generated identifier.

  On the other hand, in the second process, the above-described cache index table 330 does not hold the logical block address LBA in the index, or an identifier (here, a valid identifier) associated with the logical block address LBA. Executed when is not registered. In the second process, the generated identifier is registered in the cache index table 330 in association with the logical block address LBA in the key index.

  By executing step 903, if access to the same logical block address LBA as this time is designated thereafter, a cache hit occurs.

An example in which step 903 is executed will be described with reference to FIG.
First, in response to a cache registration request from the client apparatus 20, data A stored in the logical block address “LBA1” of the disk volume 100-1 and having no problem with leakage is cached corresponding to the disk volume 100-1. Assume that cache data is registered using the index table 330 and the cache data table 340. On the other hand, it is assumed that data A is also stored in the logical block address “LBAn” of the disk volume 100-n. However, it is assumed that the data A stored in the logical block address “LBAn” of the disk volume 100-n is not registered as cache data.

  In this state, it is assumed that the relay device 30 has received a read command for reading data from the logical block address “LBAn” of the disk volume 100-n transmitted from the client device 20. In this case, a cache miss hit occurs, and the above-described registration process in the cache index table (step 809 in FIG. 8) is executed. As a result, the identifier “hash value 1” corresponding to the contents of the data A is registered in the cache index table 330 corresponding to the disk volume 100-n in association with the logical block address “LBAn”.

  Similarly, it is assumed that the relay device 30 has received a read command for reading data from the logical block address “LBA4” of the disk volume 100-1 transmitted from the client device 20. Data A is stored in the logical block address “LBA4” of the disk volume 100-1. If the data A of the logical block address “LBA4” is not registered in the cache data table 340, unlike FIG. 6, a cache miss occurs and the registration processing (see FIG. 8 step 809) is executed. As a result, in the cache index table 330 corresponding to the disk volume 100-1, as shown in FIG. 6, the identifier “hash value 1” corresponding to the content of the data A is associated with the logical block address “LBA4”. Is registered.

  That is, in this embodiment, if i (i = 1 to n), j (j = 1 to n), x, and y are i ≠ j and / or x ≠ y, the client apparatus 20 relays When the data A of the logical block address “LBAx” of the disk volume 100-i specified by the command is registered in the relay device 30 as cache data in accordance with the cache registration command transmitted to the device 30, the disk volume When executing a read instruction that reads data A at logical block address “LBAy” of 100-j, the identifier of data A is associated with the logical block address “LBAy” in the cache index table 330 corresponding to disk volume 100-j. “Hash value 1” is automatically registered. As described above, according to this embodiment, for example, even in a thin client system in which a disk volume is prepared for each client device (or for each user who uses the client device) on the storage device 10, for each client device ( Alternatively, the cache data can be registered in a form that can be used by each client (or user) without requesting the relay apparatus 30 from the client apparatus to register the cache data for each user.

  On the other hand, when the data corresponding to the generated identifier is not registered in the cache data table 340 (NO in step 902), the index registration unit 320d stores the index in the cache index table 330 used for the cache miss hit determination. The identifier registered in association with the logical block address LBA in the middle is replaced with, for example, an invalid value (null value) (step 904). As a result, a cache miss hit occurs even when access to the same logical block address LBA as this time is designated. However, if the identifier associated with the logical block address LBA is not registered in the cache index table 330, step 904 is not executed, and the registration process to the cache index table ends.

  When the data length L of the read target data is equal to the data length of the plurality of cache blocks, the cache hit determination unit 320b may execute the cache hit determination process in step 802 as follows. That is, the cache hit determination unit 320b refers to a plurality of entries in the cache index table 330 corresponding to the data area indicated by the logical block address and the data length L, and determines whether identifiers are registered in all of them. Good. For example, if the data length L is 2a sector, the cache hit determination unit 320b holds the entry holding the logical block address LBA and the logical block address (LBA + 1) among the entries in the cache index table 330. Refer to the entry. Here, the cache hit is determined as a whole only when the cache hit is determined in all the referenced entries. On the other hand, when a cache miss hit is determined even for one entry, a cache miss hit is determined as a whole.

  The operation of the relay device 30 when a read request is transmitted from the client device 20 has been described above. The operation of the relay device 30 when a write request is transmitted from the client device 20 is the same as that in the case of a read request except that the data transfer direction is changed from the client device 20 to the storage device 10. Is omitted.

[Modification]
Next, a modification of the above embodiment will be described.
This modification is different from the above embodiment with respect to the cache registration operation. Therefore, in order to prepare an understanding that the present modification is different from the embodiment, an outline of the cache registration operation of the relay device 30 applied in the embodiment is shown below.

  When the relay device 30 receives the cache registration request from the client device 20 (step 703), the relay device 30 establishes an iSCSI session for the storage device 10 (the disk volume 100-1 thereof) to which the client device 20 is connected (step 703). 704). In this state, the relay device 30 acquires the cache registration target data from the storage device 10 (steps 705 and 706) and registers it in the cache data table 340 (steps 707 and 708). Then, the relay device 30 closes the iSCSI session (709). This iSCSI session is independent of the iSCSI session between the client apparatus 20 and the storage apparatus 10 relayed by the relay apparatus 30.

  Next, the procedure of the cache registration operation of the relay device 30 applied in this modification will be described with reference to the flowchart of FIG. In FIG. 10, the same parts as those in the flowchart of FIG. 7 are denoted by the same reference numerals.

  When receiving the cache registration request from the cache registration data selection / request transmission unit 220 of the client device 20 (step 703), the cache registration request processing unit 370 of the relay device 30 performs a session acquisition process (step A1). As a result of this session acquisition processing, the cache registration request processing unit 370 has an iSCSI session (communication) between the cache registration request source client device 20 and the storage device 10 relayed by the relay unit 310 of the relay device 30. The iSCSI session is acquired via the relay unit 310. Details of the session acquisition process will be described later.

  When the cache registration request processing unit 370 acquires an iSCSI session between the client device 20 and the storage device 10, the cache registration request processing unit 370 generates a read command for reading the cache registration target data for which cache registration is requested from the client device 20 ( Step A2). Then, the cache registration request processing unit 370 transmits the generated read command to the storage apparatus 10 via the relay unit 310 using the previously acquired iSCSI session (step A3). Here, the transmission of the read command is realized by inserting the read command between the iSCSI-PDU (during communication) relayed in the acquired iSCSI session.

  The cache registration request processing unit 370 receives the data returned as a response from the storage apparatus 10 in response to the transmission of the read command via the relay unit 310, thereby acquiring the data as cache registration target data (step 706). . The response from the storage device 10 is not relayed to the client device 20.

  Subsequent operations are the same as in the above embodiment, and processing for registering cache registration target data in the cache data table 340 as cache data (steps 707 and 708) is performed. However, in this modified example, step 709 performed in the embodiment after this processing is not performed.

Next, the procedure of the session acquisition process (step A1 in FIG. 10) will be described with reference to the flowchart in FIG.
The cache registration request processing unit 370 checks whether there is an iSCSI session between the client apparatus 20 that is the cache registration request source and the storage apparatus 10 relayed by the relay unit 310 of the relay apparatus 30 (steps A11 and A12). ). If such an iSCSI session exists (YES in step A12), the cache registration request processing unit 370 acquires the iSCSI session (step A13).

  In contrast, if there is no iSCSI session, the cache registration request processing unit 370 notifies the cache registration data selection / request transmission unit 220 of the client device 20 that the cache registration request has not been executed yet. A response is returned (step A14). Then, the cache registration request processing unit 370 waits for the establishment of the iSCSI session described above (steps A15 and A16). If this iSCSI session is established (YES in step A16), that is, if the relay of communication between the client apparatus 20 and the storage apparatus 10 is started, the cache registration request processing unit 370, for example, At that timing, the iSCSI session is acquired (step A13).

According to this modification, in addition to the same effects as in the above embodiment, the effects listed below can be obtained.
(1) It is not necessary for the relay device 30 to terminate the iSCSI session independently for cache registration. That is, it is not necessary for the relay device 30 to implement an operation as an initiator corresponding to the client device 20 (communication protocol with the storage device 10).

(2) Even when the client device 20 reserves the disk volume 100-i of the storage device 10 or when the relay device 30 cannot newly connect to the storage device 10 due to the simultaneous connection limit on the storage device 10 side. The relay device 30 can read data from the storage device 10 for cache registration.

(3) When authentication is provided for accessing the disk volume 100-i on the storage apparatus 10 side, management for that is facilitated. The reason is as follows. First, in the embodiment, in order to independently establish an iSCSI session from the relay apparatus 30 to the storage apparatus 10 for cache registration, this authentication must be passed. Authentication information must be managed in cooperation with the device 20 or the storage device 10. On the other hand, in the modified example, such management is not necessary in order to share the already set session. Moreover, in the modified example, the cache registration request can be processed asynchronously even when the relay unit 310 of the relay device 30 is not relaying.

  In addition, this invention is not limited to the said embodiment or its modification example as it is, A component can be deform | transformed and embodied in the range which does not deviate from the summary in an implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment or its modification. For example, you may delete a some component from all the components shown by embodiment or its modification.

  DESCRIPTION OF SYMBOLS 10 ... Storage apparatus (1st apparatus), 20 ... Client apparatus (2nd apparatus, 3rd apparatus), 30 ... Relay apparatus, 100-1-100-n ... Disk volume, 210 ... Driver file system, 211 ... File system, 220 ... Cache registration data selection / request transmission unit, 310 ... Relay unit, 320 ... Cache management unit, 320a ... Cache registration unit, 320b ... Cache hit determination unit, 320c ... Relay control unit, 320d ... Index registration 330: Cache index table, 340 ... Cache data table, 350 ... Cache data storage unit, 360 ... Identifier generation unit, 370 ... Cache registration request processing unit (cache registration request receiving means), 380 ... Cache storage unit.

Claims (9)

In a relay device that relays communication for data transfer between a first device that stores data and a second device that performs read / write access to the first device,
Cache storage means for storing data stored in the first device in association with an identifier corresponding to the content of the data;
A cache index table for holding an identifier corresponding to the content of data stored in the cache storage means in association with an index for specifying the data in the first device;
Cache registration request receiving means for receiving a cache registration request including an index transmitted from the third device;
A relay unit that relays communication for data transfer between the first device and the second device, wherein the cache registration request receiving unit receives the cache registration request; reads the first data designated by the index included in the cache registration request from the first device, it receives a write request including an index for read-write access to the first device from the second device If the second includes relay means for inputting and outputting the second data designated by the index included in the read and write requests to and from the second device,
Identifier generating means for generating an identifier corresponding to the content of the requested data;
In the first case, an identifier corresponding to the content of the first data is generated by the identifier generation unit, the first data is stored in the cache storage unit in association with the generated identifier, and a cache registration means for registering the generated identifier, the cache index table in association with the index for specifying the first data,
In the second case, an identifier corresponding to the data content is registered in the cache index table in association with the index included in the read / write request, and the same identifier as the identifier is registered in the cache storage unit. and determining a cache hit determination means that the cache hit has that it is, the second data designated by the index included in the read-write request exists in the cache storage means,
Wherein when it is not determined to be a cache hit, by relayed to the first device by said relay means said read and write requests, said second data designated by the index included in the read and write requests Relay control means for causing the relay means to acquire and relaying to the second device by the relay means;
Wherein a indexing means an identifier corresponding to the content of the second data relayed by said relay means for not determined to be a cache hit Ru is generated by the identifier generation unit, the generated identifier When the same data as the second data is stored in the cache storage unit in association with the same identifier , the generated identifier is associated with the index included in the read / write request. An index registration means for registering in the cache index table. The cache storage means includes
Cache data storage means for storing data stored in the first device;
A cache data table for storing storage location information indicating a storage location of the data in the cache data storage means in association with an identifier corresponding to the content of data stored in the cache data storage means;
The cache registration unit stores the first data in the cache data storage unit, and stores storage position information indicating a storage position of the first data in the cache data storage unit corresponding to the content of the first data. The first data is stored in the cache storage unit in association with the generated identifier by registering it in the cache data table in association with the generated identifier. The relay device described.   The first device that generates a read command for reading the first data specified by the index included in the received cache registration request from the first device, and that is relayed by the relay means The relay apparatus according to claim 1, further comprising a cache registration request processing unit that inserts the generated read instruction into communication between the first apparatus and the second apparatus.   The cache registration request processing means, when the cache registration request is received, when the relay means is not relaying communication between the first device and the second device, the third device 4. The relay apparatus according to claim 3, wherein a response for notifying execution completion of the cache registration request is returned to the server, and the read command is inserted into the communication after the relay of the communication is started. .   The relay apparatus according to claim 1, wherein the second apparatus includes the third apparatus. Relay comprising a cache storage means and a cache index table for relaying communication for data transfer between a first device that stores data and a second device that performs read / write access to the first device A method for registering cache data in a device executed by the device,
Receiving a cache registration request when a cache registration request including an index designating the first data stored in the first device is transmitted from the third device to the relay device; and
Reading the first data specified by the index included in the received cache registration request from the first device;
A first identifier generating step for generating an identifier corresponding to the content of the read first data;
The read first data is stored in the cache storage unit in association with the identifier generated in the first identifier generation step, and the generated identifier is designated as the first data a cache registration step of registering in the cache index table in association with the index,
Receiving a read / write request when a read / write request including an index specifying second data for read / write access to the first device from the second device is transmitted to the relay device;
With the identifier corresponding to the content of the data in the cache index table in association with the index included in the read or write request is registered, is and registered the identifier and the same identifier in the cache storage means, determining that a cache hit the second data designated by the index included in the read-write request exists in the cache storage means,
If the cache hit is not determined, the second data specified by the index included in the read / write request is transferred to the first device by relaying the read / write request to the first device. Obtaining from the device;
Relaying the acquired second data to the second device;
A second identifier generating step for generating an identifier corresponding to the content of the second data relayed because the cache hit was not determined ;
When the same data as the second data is stored in the cache storage means in association with the same identifier as the identifier generated in the second identifier step, the generated identifier is used as the read / write request. And registering it in the cache index table in association with the index included in the cache data table . The cache storage means includes
Cache data storage means for storing data stored in the first device;
A cache data table for storing storage location information indicating a storage location of the data in the cache data storage means in association with an identifier corresponding to the content of data stored in the cache data storage means;
The cache registration step includes:
Storing the first data in the cache data storage means;
Storing the storage location information indicating the storage location of the first data in the cache data storage means in association with the identifier generated in the first identifier generation step in the cache data table. A method for registering cache data in the relay device according to claim 6. The step of reading includes
Generating a read command for reading from the first device the first data specified by an index included in the received cache registration request;
7. The step of inserting the generated read command into communication between the first device and the second device relayed by the relay means, or A method for registering cache data in the relay device according to claim 7. The reading step is performed when the relay device does not relay communication between the first device and the second device when the cache registration request is received. Returning a response for notifying execution completion of the cache registration request;
The method for registering cache data in a relay device according to claim 8, wherein, when a response indicating that the execution is not completed is returned, the inserting step is executed after the start of the relay of the communication. .

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